The other side of the argument was never offered or wanted for that matter.

Gerst tiptoed around the question Cruz asked about what hardware is needed to go exploring by pumping up SLS/Orion like it's all NASA needs and then making a small remark about needing a hab to go to Mars, nothing about landers of any kind. Big black mark on him for that one.

I think that while Methane isn't as bad as storables or solids, I'm not convinced it's actually better than LH2 except in some limited situations (like when you can easily make Methane via ISRU such as on Mars). Especially with XCOR's comments that LH2 doesn't seem to be the Cryogenic Satan Juice that some people make it out to be, my take is that LH2 still makes a lot of sense for in-space large-deltaV-propulsion.

That said, while I think LH2 makes more sense, CH4 isn't as bad as most of the other alternatives, and might even win out in some corner cases.

~Jon

Doesn't methane have less boiloff?

Sure. But boiloff isn't everything. I don't think it's worth contorting a design just because some people are too afraid of the right answer.

Sure. But boiloff isn't everything. I don't think it's worth contorting a design just because some people are too afraid of the right answer.

Now that's getting personal.

No, that's me being an opinionated pain in the ***.

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Storable propellant depots could be done right now with existing technology. The engines that use storable propellants are available from more suppliers and cost a lot less too.

Yes, but stages that use cryogenic propellant depots exist right now, while appropriately sized storable propellant stages for human exploration don't. For that matter, demonstrated capability to transfer storable propellants on a scale needed for human spaceflight isn't off the shelf either. I don't think that scaling up storable propellant depots or stages has any real showstoppers, but I also don't think it's really that much easier than finishing the job on proving out cryo propellant transfer technologies.

For satellite fueling/refueling, definitely stick with storables. For refueling small upper stages (like say Launcher One) stick with the propellants they're using. But for manned spaceflight, reuse the stages with all of the experience, and just finish dotting the i's and crossing the t's on cryo propellant storage/transfer.

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Boiloff isn't everything, but neither is ISP.

I totally agree. I think that different mission elements care about different propellant attributes differently. I just happen to think that for manned deep space missions, other than Mars Ascent/Descent, that LH2 deserves serious consideration (and would likely win an honest trade in most cases, especially when ISRU and economics are factored in).

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The fact is, NASA's not planning on using either because the goal isn't to actually get into space, go anywhere or do anything.

Well sure. But admit it--you like pointless academic debates just as much as I do, or you probably wouldn't be here. ;-)

I made the mistake of reading about a Senate Commerce "hearing" held today [April 23, 2013] regarding NASA’s human spaceflight plans. While some of the points made I actually agree with, one of the witnesses (Steve Cook of Dynetics) made an argument that I think merits some skepticism. The argument, which you’ve likely seen a lot recently, goes like this "If only NASA had a stable long-term exploration program, with established destinations and dates, the private sector would be jumping all over itself to create business plans supporting NASA’s exploration efforts"” At its core, this argument and others like it seem to imply that if only we hadn’t cancelled the Constellation Program, everything would’ve been better.

Wrong.

That is, wrong in the sense that a stable NASA long-term exploration program would not be only attributed to the Constellation program.

There simply hasn't been a stable NASA long-term exploration program for forty years, so we don't really know how the private sector would have responded to it.

It's not about Constellation. It's about NASA's intent to explore. There is no intent for HSF, therefore there can be no exploration. The USG has no stated need for HSF.

His article is pretty much spot on, in that:

Quote from: Jon Goff

If Congress really wants commercial industry to more actively engage themselves in NASA’s exploration efforts, and to invest private money in ways that are synergistic with their exploration goals, they could try establishing a realistic long-term plan for NASA that fits within realistic budgets, they could try to seriously work with industry to understand what markets industry sees as viable that are also synergistic with NASA’s exploration desires, and work with them to retire the technological risks that are impeding the commercial development of those markets.

Stafford mentions that SLS is essential because it is not possible to use many small rockets because of the boiloff of LH2.

My first reaction to this was that Stafford must have just stepped out of a time machine from 1969. But then I remembered that even in the mid-1960s, people were proposing assembling Saturn V-derived, hydrogen-fuelled stages in orbit to go to Mars. In other words, even way back then serious people thought the boil-off problem was soluble.

And it's really odd for an SLS supporter to make this argument. Mars is supposedly SLS's ultimate destination. Multiple SLS launches would be needed for this. If a multi-launch lunar mission isn't possible, how can a multi-launch Mars mission be possible?

And it's really odd for an SLS supporter to make this argument. Mars is supposedly SLS's ultimate destination. Multiple SLS launches would be needed for this. If a multi-launch lunar mission isn't possible, how can a multi-launch Mars mission be possible?

Easy.. Moon doesn't require SLS, can be done with multiple launches of cheaper (and likely more reliable by then) launchers. Which is bad. Because it's not SLS.[1].

Mars does require SLS[1]. Multiple launches, but they're SLS launches... See the difference???

1 - Or so Stafford thinks

« Last Edit: 04/25/2013 03:01 pm by Lar »

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"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Ugh. As soon as anybody mentions Helium-3 it's time to change the channel.

As has been noted long ago, the appropriate substitution is s/Helium 3/snake oil/g .

Nahhh... just change the channel.

Are you sure? I thought it was a "Drink!" moment every time it was mentioned?

Randy

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From The Amazing Catstronaut on the Black Arrow LV:British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

The idea that it is "depot" vs "SLS" and an "either/or" situation has to be changed. Any ideas on how to get that through "peoples" heads?

Randy

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From The Amazing Catstronaut on the Black Arrow LV:British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

The idea that it is "depot" vs "SLS" and an "either/or" situation has to be changed. Any ideas on how to get that through "peoples" heads?

From an engineering standpoint SLS could presumably use depots, but from a budgetary standpoint they seem incompatible. Where are we going to find the budget to develop SLS, depots, and payloads?

The "political" incompatibilty seems to be the basis for the conflict, rather than any serious "budget" conflicts but given an "assumption" of conflict in the first place they DO "seem" to be mutually exclusive systems

However it is like Jon noted, SLS is going to need technologies like "boil-off" control itself among others that would be useful to either system. So there is a synergy on working both systems at the same time since there is no direct need to "add" items to the budget. As long as the research isn't too "focused" on one specific system more than neccessary it can be applied to others.About the ONLY "specific" technolgy that isn't something directly related is propellant transfer technologies, and I would argue that this is something with long term benifits we WANT to develop anyway.

The tricky part comes in getting the people who are currently lined up on either side of the "debate" to stop making it a "political" issue and get them to understand there is lots of "value-added" to both sides in developing the technology. The budget can handle a lot of technological research and development as long as it keeps an "open" approach rather than being forced to focus on a single "system" approach as has been the habit in the past.

The problem is short of going to Washington and visiting a lot of people with liberal applications of a "clue-bat" I'm not sure how to convince the necessary parties involved to get out of their ruts and start thinking longer-term instead of short-term

Randy

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From The Amazing Catstronaut on the Black Arrow LV:British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

The idea that it is "depot" vs "SLS" and an "either/or" situation has to be changed. Any ideas on how to get that through "peoples" heads?

From an engineering standpoint SLS could presumably use depots, but from a budgetary standpoint they seem incompatible. Where are we going to find the budget to develop SLS, depots, and payloads?

The "political" incompatibilty seems to be the basis for the conflict, rather than any serious "budget" conflicts but given an "assumption" of conflict in the first place they DO "seem" to be mutually exclusive systems

However it is like Jon noted, SLS is going to need technologies like "boil-off" control itself among others that would be useful to either system. So there is a synergy on working both systems at the same time since there is no direct need to "add" items to the budget. As long as the research isn't too "focused" on one specific system more than neccessary it can be applied to others.About the ONLY "specific" technolgy that isn't something directly related is propellant transfer technologies, and I would argue that this is something with long term benifits we WANT to develop anyway.

The tricky part comes in getting the people who are currently lined up on either side of the "debate" to stop making it a "political" issue and get them to understand there is lots of "value-added" to both sides in developing the technology. The budget can handle a lot of technological research and development as long as it keeps an "open" approach rather than being forced to focus on a single "system" approach as has been the habit in the past.

The problem is short of going to Washington and visiting a lot of people with liberal applications of a "clue-bat" I'm not sure how to convince the necessary parties involved to get out of their ruts and start thinking longer-term instead of short-term

Randy

Randy - in theory, I agree with you, when the issue is labeled as HLV vs depots. The problem is that the current plan has you locked into a closed system, not an open system.

While they strained to connect all the dots and make the case for each of these various and sundry activities and programs, it struck me how the witnesses and Senators were feeling around (but not touching) the biggest issue of all: Why human spaceflight? ...

Now that we sit amongst the smoldering ruins of a once-great space program, perhaps we should take time once again to re-examine this issue from a different perspective. Just as the barbarian hordes lived in squalor after the fall of Rome because they could not repair the aqueducts built by their predecessors, we gaze at reposing Saturn Vs as strange artifacts of a former golden age, now reduced to tourist attractions ...

This is the elephant in the room: Why should there be a national human spaceflight program? While this beast is clearly seen by many of us, it appears to be largely invisible to some elected and appointed officials and space experts whose concerns seem to be near-term, and focused solely on how much things cost.

Our space budget will continue to shrink because there is no compelling rationale to fly stunt missions (no matter how skillfully logic is twisted). To regain our lost footing we must begin with the understanding that becoming a space faring people is the long-term goal, not “Mars” nor the “Quest for Life Elsewhere.”

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"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci